The OEDILF (Omnificent English Dictionary In Limerick Form) is an attempt to put all definitions into, yes, limerick form. Right now you’re out of luck if you want a limerick-ified definition for, say, bottle, or (heavens!) zebra. But there are 23* definitions for aardvark, so it’s not all bad.
* some of which are still tentative, and not officially ‘approved’
(via Research Buzz)